An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive or insulative layers on a silicon substrate. One fabrication step involves depositing a filler layer over a non-planar surface, and planarizing the filler layer until the non-planar surface is exposed. For example, a conductive filler layer can be deposited on a patterned insulative layer to fill trenches or holes formed in the insulative layer. The filler layer is then planarized until the raised pattern of the insulative layer is exposed. After planarization, the portions of the conductive layer remaining between the raised pattern of the insulative layer form vias, plugs and lines that provide conductive paths between thin film circuits on the substrate.
Planarization can also be used to provide a planar layer surface for photolithography. For example, an etching step used in manufacturing integrated circuits can include depositing a photo-resist layer on an exposed surface of the substrate, and then selectively removing portions of the resist layer by a photolithographic process to provide the etch pattern on the layer. If the layer is non-planar, then photolithographic techniques of patterning the resist layer may not be suitable because the surface of the substrate may be sufficiently non-planar to prevent focusing of the photographic apparatus on the entire layer surface. The substrate surface may therefore need to be periodically planarized to restore a planar layer surface of the photolithography.
Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head of a CMP apparatus. The exposed surface of the substrate is placed against a rotating polishing disk pad or belt pad. The polishing pad can be either a “standard” pad or a fixed-abrasive pad. A standard pad has a durable roughened surface, whereas a fixed-abrasive pad has abrasive particles held in a containment media. A polishing slurry, including at least one chemically-reactive agent, and abrasive particles if a standard pad is used, is supplied to the surface of the polishing pad.